Trifluorobromomethane



Patented Nov. 21, 1950 Y TRIFLUOROBROMOMETHAN E Herbert Waterman, Los Angelca, Calif.; Beatrice Joy Waterman,v executrix of said Herbert Waterman, deceased, minor, by mesne assignments, to Minnesota, Mining & Manufacturing Company, St. of Delaware Paul, Minn., a corporation Serial No. 633,857

No Drawing. Application December 8, 1945 stein or Chemical Abstracts. The authoritative work of Albert L. Henne on Aliphatic Fluorides, (chapter 11. Gilman Organic Chemis ry. vol. I. John Wiley and Sons, New York, 1943) exhaustively discusses all known aliphatic fluorides without listing trifluorobromomethane. later work (Organic Reactions, vol. 2, John Wiley and Sons, New York, 1944) Henne discusses the preparation of aliphatic fluorides and lists all known compounds recorded anywhere in the literature up to January 1, 1941 (pages 76-91 inclusive). The only fluorobromomethanes listed In a.

. specific heat of the liquid between 3 and 30 C,

by Henne are the following: CFBra, CFzBrz,

Simons, Bond 8: MacArthur studied the preparation and properties of certain fluoromethyl compounds and attempted to prepare trifluorobromomethane (Journal of the American Chemical Society pages 3477, 3480, December 1940 They did not succeed in preparing either the trifiuorobromomethane or the trifluoroiodamethane and their conclusion, as stated by them, was as follows:

"Trifluorobromomethane and trifluoroiodamethane are judged to be unstable after numerous attempts at their preparation. I have succeeded in manufacturing trifluorobromomethane, CFsBr, and have determined that it has the following physical properties:

Its boiling point is --58.67 C. or -73.6 F. at 760 mm. Hg pressure; its freezing point is -166 0.; its critical temperature is 66.6 0.; its critical pressure is 565 pounds per square inch absolute; the logarithm of its vapor pressure (P), in pounds per square inch absolute, is equal to 5.441 minus 1650 times the reciprocal of the temperature (T) in degrees Rankine or log l P =5.44l 1650( its liquid density is as follows: at 0 F. and 71.1

pounds per square inch absolute, 1.802; at 50 F. and 160.4 pounds per square inch absolute, 1.665;

at F. and 311.7 pounds per square inch absolute, 1.456; its vapor density at 25 C. and 745 mm. H8. pressure is 5.972 srams per liter; the

is 0.196 B. t. u. per pound per degree F.; its latent heat of vaporization at the normal boiling point is 54 B. t. u. per 1b.; the ratio of heat capacity at constant pressure (Cp) to the heat capacity at constant volume (Cv) at 25 C. is 1.116, that is Cp/Cv=1.1-16 at 25 C.

It will be obvious to those skilled in the art that by reason of these properties, trifiuorobromomethane is quite useful as a heat transfer medium, particularly as a refrigerant for in addition to the characteristics noted, the material is non-inflammable and is non-toxic to humans. It has a pleasant aromatic odor. The foregoing properties were determined on apparatus of such accuracy that the values given are suitable only for commercial utilization of the material; they are not of that accuracy usually associated with the values of pure science and to which the term scientific accuracy is applied.

To prepare the material a steel pressure vessel was made of a piece of 3 inch standard black iron pipe, 12 inches long threaded at each end.

At its bottom end it was closed with a threaded cap. At its top, a three inch to half inch bell reducer was fitted. A thermometer well of oneeighth inch pipe was brazed to the outside of the pipe near the bottom. A reflux condenser consisting of a four foot length of half inch pipe was threaded for attachment to the bell reducer. The half inch pipe carried two separate water jackets, each approximately two feet in length and each of two and one-half inch diameter, the jacketsbeing held in place with rubber stoppers. At the top of the half inch pipe 9. T fitting was placed carrying a suitable pressure gauge and a needle valve. Suitable attachments were provided for circulating tap water through the lower water jacket and ice cooled water through the upper water jacket.

A mixture consisting of live mols (1658.35 grams) of carbon tetrabromide was intimately mixed with seven and one-half mols (1340.70 grams) of anhydrous sublimed crystals of antimony trifiuoride. This mixture was placed in the pressure vessel and the bell reducer screwed into place. One and one-half mols of dry bromine (239.74) grams) were then added to the vessel and the reflux condenser was attached.

The pressure vessel was then heated to a tem perature between and 200 C. while the pressure was maintained between 60 and '80 pounds gauge by adiusting the steel needle valve carried by the "r. The heating under pressure was continued until no more gas was given 011 by the reaction mixture, approximately 24 hours. The gas derived from the reflux condenser was scrubbed through two caustic scrubbers, dried and condensed with Dry Ice. The crude mixture re- 3. The process or claim 2 wherein the method includes the heating of a mixture comprising proportionally 5 mole of carbon tetrabromide, 7 mole of antimony trifluoride and 1% mols or brocovered consisted of ninety-five mol percent of 5 mine.

HERBERT WATERMAN.

REFERENCES CITED The following references are of record in the 10 file of this patent:

UNITED STATES PATENTS eter column. Number Name t I claim: Re. 19,265 Midgley et a1 Aug. 7, 1934 1. The compound, triiluorobromomethane, 15 2.110.369 Leicester Mar. 8, 1938 having the formula.CF.:Br. 2.398.181 Johnson Apr. 9, 1946 2. The method of preparing trifluorobromomethane comprising heating a mixture of carbon tetrabromide, antimony trifluoride and bromine to a temperature of 180-220 C. under a pressure of 60-80 pounds gauge for a period sufficient to form trifluorobromomethane and recoverin the trifluorobromomethane.

OTHER REFERENCES Rathsburg, "Ber. deutsch. Chem. Ga," vol. 51,

20 pages 669672 (1918). 

1. THE COMPOUND, TRIFLUOROBROMOMETHANE, HAVING THE FORMULA, CF3BR.
 2. THE METHOD OF PREPARING TRIFLUOROBROMOMETHANE COMPRISING HEATING A MIXTURE OF CARBON TETRABROMIDE, ANTIMONY TRIFLUORIDE AND BROMINE TO A TEMPERATURE OF 180*-220*C. UNDER A PRESSURE OF 60-80 POUNDS GAUGE FOR A PERIOD SUFFICIENT TO FORM TRIFLUOROBROMOMETHANE AND RECOVERING THE TRIFLUOROBROMOMETHANE. 